The invention concerns an internal combustion engine comprising a system for secondary air charging comprising an intake air conduit, a combustion unit, an exhaust gas conduit, a throttle, a turbo-engine, and a compressor, wherein the throttle is arranged in the intake air conduit, wherein the turbo-engine is connected correspondingly to the intake air conduit by a supply conduit upstream and by a discharge conduit downstream of the throttle, wherein the turbo-engine is connected in operative connection to the compressor, and wherein the compressor is connected with a connecting line to the exhaust gas conduit. The invention further relates to a method for operating an internal combustion engine with a system for secondary air charging.
DE 42 19 267 A1 discloses a system for secondary air charging in an internal combustion engine. The system for secondary air charging is arranged in an intake conduit of the internal combustion engine. By charging fresh air into the exhaust gas, the exhausted pollutants can be reduced. In the intake conduit a throttle for adjusting the flow rate of the flow to the internal combustion engine is present. By means of the throttle, a differential pressure is generated that is utilized for driving a turbo-engine. The turbo-engine is provided as a motor for a compressor that charges fresh air (secondary air) into the exhaust gas conduit.
Charging secondary air into the exhaust gas is important after starting the internal combustion engine in order not to surpass the legally prescribed exhaust gas values. After starting the internal combustion engine, several crankshaft revolutions are required until a satisfactory differential pressure is generated for driving the turbo-engine. The speed of the turbo-engine increases gradually until the maximum working engine speed is achieved. In this time period, not enough secondary air is charged into the exhaust gas so that the exhaust gas values do not fulfill the legal requirements.
Moreover, DE 100 64 481 discloses an internal combustion engine with secondary air charger and a method for controlling the secondary air charger. The secondary air charger conveys fresh air into the exhaust gas area. The fresh air that is compressed by the secondary air charger exhibits a temperature increase downstream of the compressor. On the other hand, a temperature drop occurs in the case of air expanded by the turbine. These temperature values are acquired and evaluated so that conclusions can be drawn in regard to the conveying performance. Accordingly, a control of the secondary air charger can be realized. After the internal combustion engine has been started, slowly a vacuum is created that leads to a gradual running up of the secondary air charger. Until the secondary air charger has reached its working range so as to develop its full output, a longer period of time elapses.
DE 102 35 341 discloses an internal combustion engine comprising a secondary air charger for charging secondary air into an exhaust gas pipe of the internal combustion engine. The function of the secondary air charger can be monitored by a testing procedure. For this purpose, a control valve is provided that is arranged in a bypass to a fresh air conduit; after its actuation, the turbine is loaded with fresh air. In this embodiment, the turbine also requires some time until it reaches its working range.
It is an object of the invention to provide an internal combustion engine with a system for secondary air charging with which charging of fresh air (secondary air) can be realized reliably and inexpensively, which can be mounted in tight spaces and reaches the working range quickly.